Light guides are wave guides configured to guide visible light between two interfaces via total internal reflection. One type of light guide comprises a wedge-like structure, also termed a wedge light guide, configured to direct light between an interface located at one side edge of the wedge and another interface located at a major face of the wedge. Light that enters the wedge at the side edge interface is internally reflected until reaching a certain angle relative to the interface at the major surface. This allows a relatively small image projected at the side edge interface to be displayed as a relatively larger image on the major face interface of the wedge.
Wedge light guides can utilize special ports called optical concentrators. Optical concentrators are utilized to inject light into the wedge light guide and can be designed to reduce light loss over short distances. Typically, a wedge light guide is first constructed and then, after constructed, optical concentrators are physically mounted on, or otherwise affixed to the wedge light guide. Because of design and operability considerations, placement of the optical concentrators utilizes a high degree of precision.
Using wedge light guides, flat panel displays, such as backlit liquid crystal displays (LCDs) and other imaging-based devices can be designed.